1. Field of the Invention
The present invention relates generally to pressure transducers and pertains, more particularly, to in-line pressure transducers.
2. Discussion of Related Art
Injection molding machines are used to manufacture plastic and metal parts. Injection molding machines typically include a reservoir of molten plastic and a nozzle through which the molten plastic is forced at high pressures into a mold. The plastic is thereafter packed and cooled to form a part. In the manufacture of such parts, it is desirable to maintain the injected melt pressure constant so that the part is formed accurately. Without maintaining the pressure constant, the structural accuracy of the formed part may suffer. For example, the resulting part may include voids, ripples, or other dimensional inaccuracies.
As such, there is a need for pressure transducers which can accurately measure the pressure of molten plastic as it is forced from the tip of an injection molding machine. Because of the operating parameters of injection molding machines, pressure transducers used therein must be able to measure pressure accurately while withstanding pressures within the range of 40,000-50,000 psi and temperatures up to approximately 500.degree. C. Additionally, such pressure transducers are faced with the following constraints: 1. the pressure transducer should have low working stresses to avoid metal fatigue cracking under repetitive cyclic loading; 2. the pressure transducer, for economic practicality, should be physically arranged such that it can easily be integrated within the chamber/nozzle area of injection molding machines; and 3. the pressure transducer should not disrupt the plastic flow or have pockets where plastic will remain and eventually degrade and cause staining of the parts.
Accordingly, a general object of the present invention is to provide an injection molding machine pressure transducer which can accurately measure pressures of molten plastic within such machines.
A further object of the present invention is to provide an injection molding machine pressure transducer which is easily integratable with existing injection molding machines.